Coupler for Threaded Reinforcing Bar and Threaded Reinforcing Bar Including the Coupler

FIELD OF THE DISCLOSURE The present invention relates to a coupler for a threaded reinforcing bar, and particularly to a coupler to which end portions of threaded reinforcing bars facing each other are inserted, the coupler being fastened to the reinforcing bars in order to prevent loosening of the reinforcing bars and the coupler and make the reinforcing bars through which an axial force is transmitted long. The present invention also relates to a threaded reinforcing bar including the coupler.

BACKGROUND

OF THE DISCLOSURE When reinforced concrete is used to construct a building or a civil engineering structure, a deformed reinforcing bar (threaded reinforcing bar or bamboo-shaped reinforcing bar) used as a concrete reinforcing material is manufactured to have a standard length of, for example, 12 meters in consideration of convenience of transporting from shipping from a factory to a construction site. However, in use, in order to correspond to a size of a building to which the deformed reinforcing bar is applied or a length of a position to which the deformed reinforcing bar is applied, the deformed reinforcing bar is often extended at the construction site. In both cases of a threaded reinforcing bar and a bamboo-shaped reinforcing bar (a bamboo-shaped reinforcing bar is out of the scope of the present invention), the reinforcing bar is molded by being gradually deformed by calibers formed on a roll in a rolling process, and the roll becomes rough or worn even little by little. Although the roughness can be removed by surface grinding for continuous using, a decrease in a roll diameter is inevitable, and a thread pitch varies even slightly depending on a manufacturing period. On the other hand, a tooth shape formed in a bonding hole of the coupler is formed by cast molding in consideration of a molding tolerance of the reinforcing bar while being made to correspond to the thread pitch of a normal dimension of the reinforcing bar. Accordingly, although meshing can be achieved by absorbing a difference in the screw pitch between the coupler and the reinforcing bar, a gap in the meshing is inevitably remained. For preventing looseness, the gap between tooth surfaces is filled with grout (for example, mortar), or, for fall prevention, a small screw is set to erect toward a surface of the reinforcing bar from the outside of the coupler. Examples of the former case are disclosed in Patent Documents 1 and 2 and examples of the latter case are disclosed in Patent Documents 3 and 4. In any of the cases, attempting to make fastening perfect causes a long length of the coupler and an increased fastening load. Therefore, a coupler is desired, in which torque management (achievement of fastening with a small torque and even fastening force) is easy, the torque management showing an effect of preventing occurrence of looseness or fall. PRIORITY ART DOCUMENTS Patent Documents Patent Document 1: U.S. Pat. No. 4,666,326. Patent Document 2: Japanese Patent Application Publication No. 2018-178365. Patent Document 3: U.S. Pat. No. 5,046,878. Patent Document 4: U.S. Pat. No. 7,107,735.

SUMMARY

OF THE DISCLOSURE Problems to be Solved The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a coupler for bonding threaded reinforcing bars facing each other by using galling of screw threads with respect to each other, without necessarily introducing grout or a screw lock agent to a sleeve, and a threaded reinforcing bar including the coupler. Means for Solving Problems With reference to FIG. 1 , a first aspect of the present invention is a coupler for a threaded reinforcing bar to which end portions of reinforcing bars 4 L, 4 R facing each other are inserted, the coupler being fastened to the reinforcing bars 4 L, 4 R in order to prevent loosening of the reinforcing bars and the coupler and make the reinforcing bars through which an axial force is transmitted long, wherein a coupler 10 includes one main cylinder 11 , and two sub-cylinders 12 , 13 threadingly attached to an outer periphery of a left half body and an outer periphery of a right half body of the main cylinder 11 in a right and left symmetrical posture, a hole in an axial direction formed in the inside of the main cylinder 11 is a vertically passing screw hole H 5 to which a thread M 4 of the reinforcing bars 4 L, 4 R is screwed, outer peripheral screws 6 , 7 being concentric with the vertically passing screw hole H 5 and having a larger diameter than the vertically passing screw hole H 5 are formed in the outer peripheries of the right and left half bodies, end portion male screws M 6 , M 7 are provided in the outer peripheral screws 6 , 7 , the end portion male screws M 6 , M 7 have a phase that matches a phase of a female screw F 5 of the vertically passing screw hole H 5 , and have pitches P 6 , P 7 that are different from a screw pitch P 4 of the thread M 4 of the reinforcing bars 4 L, 4 R, the sub-cylinders 12 , 13 include sleeve portions 8 , 9 including end portion female screws F 8 , F 9 threadingly attached to the end portion male screws M 6 , M 7 , and nut portions 14 , 15 being coaxial with the sleeve portions and formed integrally with one side ends of the sleeve portions, and the nut portions 14 , 15 are formed with nut portion female screws F 14 , F 15 to which the thread M 4 of the reinforcing bars 4 L, 4 R is screwed, the nut portion female screws F 14 , F 15 having a phase that matches a phase of the end portion female screws F 8 , F 9 . As shown in FIG. 12 , a second aspect of the present invention is a coupler for a threaded reinforcing bar comprising a main cylinder 11 A and sub-cylinders 12 A, 13 A whose female and male of screws are inversed from female and male of screws of the main cylinder 11 and the sub-cylinders 12 , 13 , and a desired lock using galling is enabled. As shown in FIG. 6 , the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder 11 are formed with end portion male screws M 6 , M 7 having pitches P 6 , P 7 larger than a pitch P 4 of the thread M 4 of the reinforcing bars. As shown in FIG. 11 ( b ) , the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder 11 are formed with end portion male screws M 6 , M 7 having pitches P 6 , P 7 smaller than a pitch P 4 of the thread M 4 of the reinforcing bars 4 L, 4 R. As shown in FIG. 12 , an inner hole of the left half body and an inner hole of the right half body of the main cylinder 11 are formed with end portion female screws F 6 , F 7 having pitches P 6 , P 7 larger than a pitch P 4 of the thread M 4 of reinforcing bars 4 L, 4 R. In addition, an inner hole of the left half body and an inner hole of the right half body of the main cylinder 11 A are formed with end portion female screws F 6 , F 7 having pitches P 6 , P 7 smaller than a pitch P 4 of the thread M 4 of the reinforcing bars 4 L, 4 R. As shown in FIG. 4 , an outer surface of a longitudinal center portion of the main cylinder 11 is formed with a reaction receiving surface 11 C used in application of a desired torque to the nut portions 14 , 15 . The longitudinal middle portion of the main cylinder 11 is formed with a slit 17 extending in the axial direction through which a distal end position of the reinforcing bars 4 L, 4 R that have been inserted can be visually checked. A slit 18 having the same shape as a shape of the slit 17 is formed at a position facing the slit 17 . As shown in FIG. 11 ( c ) , an end portion of the reinforcing bar in a side opposite to the coupler includes a bending portion 25 that exhibits a fixation plate function. Advantageous Effects of the Invention According to the above-described first aspect, since the coupler includes the main cylinder and the two sub-cylinders having a right and left symmetrical posture, reinforcing bars to be connected are respectively bonded with equivalent components and can be fastened by torque loading operation in a similar manner. Even when there is a difference within a manufacturing tolerance in thread pitches, if the reinforcing bars have a thread within a molding tolerance, homogenization of fastening of reinforcing bars can be achieved. Since there is a difference in the pitch between the outer peripheral screws of the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder and the thread of the reinforcing bar, a frictional force acting on a screw surface becomes large due to an increase in a screw surface contact pressure that a screw thread having a small pitch receives, along with screw advancement of the screw. When surface roughness of a screw thread occurs due to galling caused by pressurization, even when it is slight surface roughness, screw advancement or retreat thereafter is inhibited, so that releasing of over-threading of the screw thread does not occur anymore unless a reverse torque corresponding to a load torque acts. According to the above-described second aspect, since there is a difference in the pitch between the end portion female screws of the inner hole of the left half body and the inner hole of the right half body of the main cylinder and the thread of the reinforcing bar, a frictional force acting on a screw surface becomes large due to an increase in a screw surface contact pressure that a screw thread having a small pitch receives, along with screw advancement of the screw. When surface roughness of a screw thread occurs due to galling caused by pressurization, even when it is slight surface roughness, screw advancement or retreat thereafter is inhibited. Since the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder are formed with the outer peripheral screw having a pitch larger than a pitch of the thread of the reinforcing bar or formed with the outer peripheral screw having a pitch smaller than a pitch of the thread of the reinforcing bar, due to this pitch difference, a large frictional force acting on a surface of the screw due to a screw surface contact pressure acts and firm fastening is made with a galling of the screws. Regarding convenience of fastening, in the coupler according to the present invention, fastening can be made without rotating the threaded reinforcing bar. Since the inner hole of the left half body and the inner hole of the right half body of the main cylinder are formed with the end portion female screw having a pitch larger than a pitch of the thread of the reinforcing bar or formed with the end portion female screw having a pitch smaller than a pitch of the thread of the reinforcing bar, due to this pitch difference, a large frictional force acting on a surface of the screw due to a screw surface contact pressure acts and firm fastening is made with a galling of the screws. By forming a reaction receiving surface on an outer surface of a center body being a longitudinal center portion of the main cylinder, receiving a reaction force when a desired torque is applied to the nut portion becomes easy. When a slit extending in the axial direction is formed in a center body being a longitudinal middle portion of the main cylinder, a distal end position of the inserted reinforcing bar can be checked. When another slit having the same shape as the slit is formed in a position facing the slit, viewing through is enabled and checking of the distal end position of the inserted reinforcing bar is facilitated. By providing a bending portion in the end portion in the side opposite to the coupler of the reinforcing bar, a fixation plate function can be exhibited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing completion of fastening of reinforcing bars by a coupler for a threaded reinforcing bar according to a first embodiment of the present invention. FIG. 2 is a view showing a former half process of a procedure of fastening reinforcing bars by the coupler for a threaded reinforcing bar. FIG. 3 is a view showing a latter half process of fastening reinforcing bars including processing of meshing of both reinforcing bars and pitch alignment using a gauge. FIG. 4 is a perspective view of appearance of a main cylinder. FIG. 5 is a perspective view of a threaded reinforcing bar along and a partially enlarged view thereof. FIG. 6 is a vertical cross-sectional view of the main cylinder. FIG. 7 is a perspective view of appearance of sub-cylinders. FIG. 8 is a vertical cross-sectional view of the sub-cylinders. FIG. 9 is a view of a screw end surface with a point Q indicating a start of meshing in the sub-cylinders. FIG. 10 is a view showing an equal pitch setting process using a gauge. FIG. 11 is a view showing a latter half process of a procedure of fastening reinforcing bars having different pitch modes and is a view of application to a reinforcing bar having a fixation action. FIG. 12 is a view showing completion of fastening of reinforcing bars according to a second embodiment of the present invention in which female and male of threading attachment of the main cylinder and the sub-cylinders are made inversed.

DETAILED DESCRIPTION

OF THE EXEMPLARY EMBODIMENTS Hereinafter, a coupler for a threaded reinforcing bar according to the present invention will be described with reference to the drawings showing embodiments thereof. This invention is used for fastening threaded reinforcing bars 4 L, 4 R facing each other as shown in FIG. 2 ( a ) in a manner shown in FIG. 3 ( c ) . That is, this present invention is to bond rigidly reinforcing bars by using galling of screw threads in either case of using grout and not using grout. A coupler 10 , in which end portions facing each other of two reinforcing bars 4 L, 4 R shown in FIG. 2 ( a ) are inserted, prevents loosening of screwing with the reinforcing bar 4 to extend the length of the reinforcing bar through which an axial force is transmitted. This coupler 10 includes one main cylinder 11 and sub-cylinders 12 , 13 arranged in right and left symmetrical, that is, provided for each reinforcing bar. Accordingly, the coupler 10 consists of three components and is significantly simple and less bulky. All of the components are rigid bodies made of metal and in principle, they are casting as described later. The main cylinder 11 is a cylinder having appearance shown in FIG. 4 with an outer diameter of about 1.4 times a diameter of the reinforcing bar, for example. A center body 11 C forms a polygonal surface (hexagonal face in the drawing) that enables reverse torque application at the time of fastening. Outer surfaces of a left half body and a right half body of the main cylinder 11 are formed with male screws M 6 , M 7 as described later. A hole in the axial direction formed in the inside of the main cylinder 11 is a through hole H 5 (see FIG. 4 ) that is screwed with a thread M 4 (see FIG. 5 ) of the reinforcing bars 4 L, 4 R even if there is a meshing gap (including a rear gap). This through hole H 5 is generally a right screw in both the left half body and the right half body. The through hole H 5 includes a sufficient number of female screws F 5 (see FIG. 6 , for example, five or six) for meshing and bonding with the screw thread M 4 of the reinforcing bars 4 L, 4 R that exhibit a predetermined fastening performance. The pitch of the thread from one opening end to the other opening end of this through hole H 5 is fixed. The screw phase is the same in the left half body and the right half body regardless of whether the spiral in the through hole H 5 is interrupted (not shown) or not (in the portion having a viewing hole of the E part in FIG. 6 , the through hole H 5 is not interrupted). That is, even one reinforcing bar 4 can be screwed into and penetrate through the screw hole H 5 (see FIG. 2 ( c ) ). This is because this screw hole H 5 and nut portion female screws F 14 , F 15 described later of the sub-cylinders 12 , 13 described above form screws having screw phases matching each other in a state of being covered with the sub-cylinders 12 , 13 up to a deep portion in the depth as shown in FIG. 3 ( b ) . Regarding prefixes of signs, H refers to a hole portion, M refers to a male screw, F refers to a female screw, and P refers to a pitch. Also hereinafter, members and portions will be described such that they can be recognized easily. It is needless to say that the number of female screws F 5 (see FIG. 6 ) is sufficient for achieving meshing necessary for fastening if the reinforcing bar is one in which a molding tolerance in consideration of wear of a molding roll is allowed. That is, the female screw F 5 of the through hole H 5 existing in the inside of the main cylinder 11 has a number of spirals that enables normal threading attachment without interference of tooth surfaces while satisfying meshing of a desired pitch number in either case where the reinforcing bar has the tolerable maximum pitch or the tolerable minimum pitch. For example, when a target is a reinforcing bar having D35 (a nominal diameter is 35 mm), the main cylinder 11 needs meshing of an amount of 5 or 6 pitches in one side and 12 pitches for right and left. Even when a reinforcing bar end abutting space E (see FIG. 6 ) at the center is added to the pitches, it is sufficient that the coupler has a length of about 300 mm at most. As shown in FIG. 6 , in the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder 11 are formed with outer peripheral screws 6 , 7 being concentric with the through hole H 5 , having a phase matching a phase of the through hole H 5 , and having pitches P 6 , P 7 (see FIGS. 4 and 6 ) not equal to a pitch P 4 (see FIG. 5 ) of the thread M 4 of the reinforcing bar 4 . For example, a dimension of P 7 =P 4 +2 mm is selected. The difference of 2 mm is given for generating galling and enabling absorbing of accumulated pitch molding tolerances of an amount of several pitches in the case that there is such accumulation of pitch molding tolerance (for example, ±0.2 mm each) of the reinforcing bar. The sub-cylinders 12 , 13 have appearance as shown in FIG. 7 . The sub-cylinders 12 , 13 include sleeve portions 8 , 9 respectively covering the outer periphery (see FIG. 6 ) of the left half body and the outer periphery of the right half body of the main cylinder 11 , and nut portions 14 , 15 being coaxial with the sleeve portions and formed integrally with one side end of the sleeve portions. In the inside of the sleeves, sleeve inner peripheral screws F 8 , F 9 (see FIG. 2 ( b ) and FIG. 7 ) meshing with the outer peripheral screws 6 , 7 (see FIGS. 4 and 6 ) described above are provided. The nut portions 14 , 15 are formed with nut portion female screws F 14 , F 15 (see FIGS. 2 ( b ) , 7 , and 8 ) to which the thread M 4 of the reinforcing bar having a phase matching a phase of the sleeve inner peripheral screws F 8 , F 9 is screwed. That is, the screw pitches P 14 , P 15 (see FIG. 3 ( c ) ) of the nut portion female screws F 14 , F 15 are made to be equal to the thread pitch P 4 in the reinforcing bar tolerable minimum molded article (this means an article conforming to a reference dimension of a manufacturing drawing). The number of the threads meshing with the reinforcing bar 4 by the nut portion female screws F 14 , F 15 are set to the number of threads of meshing that enables a fastening effect in the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder 11 . Accordingly, as shown in FIG. 2 ( b ) , in the coupler 10 , the through hole H 5 and the nut portion female screws F 14 , F 15 are formed, the nut portion female screw F 14 , the female screw F 5 of the through hole H 5 , and the nut portion female screw F 15 form a screw hole of the fixed pitch P 4 and end portions of the left and right reinforcing bars 4 L, 4 R can be enclosed. As shown in FIG. 3 ( b ) , as a result, all phases of the female screw F 5 of the through hole H 5 , the end portion male screws M 6 , M 7 of the outer peripheral screws 6 , 7 , the sleeve inner peripheral female screws F 8 , F 9 , and the nut portion female screws F 14 , F 15 are made to be the same. The same phase means that a rotation angle of a screw end at the time of start of meshing of screws is the same. That is, the rotation here refers to a rotation angle θ in FIG. 9 at a time point when the distal end of the male screw is caused to fall into the opening of the female screw and at a time point when meshing starts. The same rotation angle at the time of start of meshing, that is, the same rotation angle position of meshing start results in that meshing is collectively started by an advancing angle (for example, 2π/3 rad 120 degrees) from a point U with reference to an angle at which a threading attachment (spiral) start point Q exists. According to a screw group having such a configuration, by applying a desired torque enabling fastening strength to be held to the nut portions 14 , 15 (see FIG. 7 ) and causing the nut portions 14 , 15 to rotate and perform screw advancement while obtaining a reaction force with the reaction force torque application surface 11 C (see FIG. 4 ) of a polygonal cross-section, the nut portion female screws F 14 , F 15 of the nut portion 14 , 15 tightly pressure-contacts with the thread M 4 of the reinforcing bars 4 L, 4 R to exhibit a frictional force (see FIG. 3 ( c ) ), this means occurrence of galling). As a result, unintended rotation and axial displacement of the reinforcing bar can be prevented. As shown in FIG. 6 , the through hole H 5 at the longitudinal middle portion of the main cylinder 11 is formed with a slit 17 extending in the axial direction through which the distal end positions of the inserted reinforcing bars 4 L, 4 R can be viewed for observation. When a slit 18 having the same shape as the shape of the slit 17 is formed at a position facing the slit 17 , an abutting end of the reinforcing bar 4 can be easily recognized by viewing through the slits so that the insertion depth of the reinforcing bar is not misjudged. It is not easy by cutting (mechanical processing) operation to achieve that the outer peripheral screws 6 , 7 (see FIG. 6 ) formed in the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder 11 have a phase matching the phase of the female screw F 5 of the through hole H 5 , and that the nut portion female screws F 14 , F 15 (see FIG. 7 ) to which the thread M 4 (see FIG. 5 ) of the reinforcing bar is screwed have a phase matching the phase of the sleeve inner peripheral screws F 8 , F 9 (see FIG. 3 ( b ) ). As can be seen in FIG. 3 ( b ) , all tooth surfaces need to be simultaneously subjected to initial meshing, but the processing for achieving this should be casting. Since this matter does not relate directly to the gist of the present invention, and therefore, is not described here. Next, a procedure of fastening reinforcing bars will be described. With reference to FIG. 2 ( a ) , the main cylinder 11 and the two sub-cylinders 12 , 13 are arranged at a connection portion of two threaded reinforcing bars 4 L, 4 R. It is sufficient that the sub-cylinders 12 , 13 to be used are ones having the same specifications (the same nominal diameter, pitch, phase, and the like). The sub-cylinders 12 , 13 are simply arranged in right and left symmetrical. First, as shown in FIG. 2 ( b ) , the sleeve inner peripheral screws F 8 , F 9 are allowed to mesh with the outer peripheral screws M 6 , M 7 and threadingly attached deep to one side of the main cylinder 11 so as to make the screw phases match and threadingly attached deep to the other side of the main cylinder 11 so as to make the screw phases match. The center body 11 C has a rectangular cross-shape (see FIG. 4 ) and the sub-cylinders 12 , 13 have shape and dimension that cannot cover up to the center body 11 C, but covers almost the entire left half body and right half body. The sub-cylinders 12 , 13 are arranged in proximity to each other although they do not cover the slits 17 , 18 . After the initial meshing, the threaded reinforcing bar 4 R is caused to approach the threaded reinforcing bar 4 L (see FIG. 2 ( c ) ). The threaded reinforcing bar 4 L is caused to project from the assembled coupler 10 by about one pitch as shown in FIG. 3 ( a ) until a distal end 4 Le of the threaded reinforcing bar 4 L protrudes, for example, and a screw-shaped gauge 19 (see FIG. 10 ) is applied, so that continuity of spiral of the screw is held. That is, uneven phases are prevented. As shown in FIG. 3 ( b ) , the entire coupler 10 is caused to move (to right by rotation). Since the nut portion female screw F 14 of the sub-cylinder 12 , the female screw F 5 of the through hole H 5 of the main cylinder 11 , and the nut portion female screw F 15 of the sub-cylinder 13 continue, the movement operation to the threaded reinforcing bar 4 L is not difficult. That is, the end of the threaded reinforcing bar 4 R and the end of the threaded reinforcing bar 4 L facing each other are made to hold a predetermined gap E (see FIG. 3 ( b ) ) and then, the coupler 10 is caused to perform screw advancement toward the threaded reinforcing bar 4 R. Whether the end of the threaded reinforcing bar 4 L and the end of the threaded reinforcing bar 4 R facing each other are located at the through hole H 5 as shown in FIG. 3 ( b ), ( c ) is checked by viewing through the slits 17 , 18 (see FIG. 4 ). When it is checked that they are correctly located, the sub-cylinders 12 , 13 are caused to perform reverse rotation to separate in directions indicated by arrows 21 , 22 . Then, the sub-cylinders 12 , 13 move so as to follow the outer peripheral screws 6 , 7 , and the nut portion female screws F 14 , F 15 attempt to move so as to be guided by the threaded reinforcing bar. When the sub-cylinder is rotated once, for example, the movement amount caused by guiding by the outer peripheral screw 6 is one pitch P 6 . At the same time, the sub-cylinders 12 , 13 have to move by P 4 +2 mm (=P 6 ) since they are screwed to the threaded reinforcing bar 4 R (see FIG. 6 ). Although this is impossible since the sub-cylinders 12 , 13 are rigid bodies, when a torque of galling is applied to the screw thread of the coupler 10 , interference of tooth surfaces occurs between the nut portion female screws F 14 , F 15 to which the thread of the reinforcing bar is screwed and the thread M 4 of the reinforcing bar 4 R, and a damage occurs, so that the nut portion female screws F 14 , F 15 are in a galling state due to the screw of the reinforcing bar 4 R to which the nut portion female screws F 14 , F 15 are screwed. This means that the nut portion female screws F 14 , F 15 cannot perform not only screw advancement but also retreat (be loosened) anymore. In fastening release operation in a case of finding a fastening error or the like, when the screw thread can be repaired even though it cannot be perfectly repaired, the lock state is released. In contrast to the above example, in a case of P 4 =P 6 +2 mm (that is, P 6 =P 4 −2 mm), the sub-cylinders 12 , 13 are rotated to right and caused to approach in directions indicated by arrows 23 , 24 as shown in FIG. 11 ( b ) . Since the nut portion female screws F 14 , F 15 attempt to move by being guided by the threaded reinforcing bar 4 R, so that galling in the outer peripheral screws M 6 , M 7 first occurs. The sub-cylinders 12 , 13 also attempt to move along the outer peripheral screws 6 , 7 . This is because, when the sub-cylinders 12 , 13 move by an amount of one rotation, for example, along the male screw M 4 of the reinforcing bar, the sub-cylinders 12 , 13 have to move by the pitch P 6 +2 mm along the outer peripheral screw 6 . As can be understood from these explanations of operation, although there is a case of moving both the threaded reinforcing bars 4 L, 4 R in the axial direction, there is no need to cause the threaded reinforcing bars 4 L, 4 R to rotate for screw advancement or screwing. That is, fastening is achieved only by rotation operation of the main cylinder 11 and the sub-cylinders 12 , 13 . Essential configurations for achieving the operation described above are represented as below. With reference to FIG. 1 , a coupler to which end portions facing each other reinforcing bars 4 L, 4 R having the same specifications (the same diameter, the same pitch, and the same screw phase) are inserted, the coupler being fastened to the reinforcing bars in order to prevent loosening of the reinforcing bars and the coupler and make the reinforcing bars through which an axial force is transmitted long, in which the coupler 10 includes one main cylinder 11 , and two sub-cylinders 12 , 13 threadingly attached to an outer periphery of a left half body and an outer periphery of a right half body of the main cylinder 11 in a right and left symmetrical posture, a hole in an axial direction formed in the main cylinder 11 is a vertically passing screw hole H 5 to which a thread M 4 of the reinforcing bars 4 L, 4 R is screwed, outer peripheral screws 6 , 7 being concentric with the vertically passing screw hole H 5 and having a larger diameter than the vertically passing screw hole H 5 are formed in the outer peripheries of the right and left half bodies, end portion male screws M 6 , M 7 are provided in the outer peripheral screws 6 , 7 , the end portion male screws M 6 , M 7 have a phase that matches a phase of a female screw F 5 of the through hole H 5 , and have pitches P 6 , P 7 that are different from a screw pitch P 4 of the thread M 4 of the reinforcing bars 4 L, 4 R, the sub-cylinders 12 , 13 include sleeve portions 8 , 9 including end portion female screws F 8 , F 9 threadingly attached to the end portion male screws M 6 , M 7 , and nut portions 14 , 15 being coaxial with the sleeve portions and formed integrally with one side ends of the sleeve portions, and the nut portions 14 , 15 are formed with nut portion female screws F 14 , F 15 to which the thread M 4 of the reinforcing bars 4 L, 4 R is screwed, the nut portion female screws F 14 , F 15 having a phase that matches a phase of the end portion female screws F 8 , F 9 . Here, in a case of (1) P 8 =P 14 +2 mm or P 9 =P 15 +2 mm, when the sub-cylinders 12 , 13 are separated from each other, galling occurs in P 14 , P 15 . In a case of (2) P 14 =P 8 +2 mm or P 15 =P 9 +2 mm, when the sub-cylinders 12 , 13 are caused to approach each other, galling occurs in P 8 , P 9 . Since P 4 ≢P 14 ≢P 15 and P 6 ≢P 7 ≢P 8 ≢P 9 are set, galling occurs in a chain reaction manner sometimes in meshing portions having a pitch difference excluding normal meshing portions. As described above, according to the present invention, a lock using galling due to strong contact between screw tooth surfaces is achieved. In the present invention, a desired lock using galling can be achieved not only in the configuration of FIG. 1 but also in the configuration as shown in FIG. 12 in which female and male of the screws of the main cylinder 11 and the sub-cylinders 12 , 13 are inversed. The configuration can be represented as below. A coupler to which end portions of reinforcing bars 4 L, 4 R facing each other are inserted, the coupler being fastened to the reinforcing bars in order to prevent loosening of the reinforcing bars and the coupler and make the reinforcing bars through which an axial force is transmitted long, in which the coupler 10 A includes one main cylinder 11 A, and two sub-cylinders 12 A, 13 A screwed to an inner hole of a left half body and an inner hole of a right half body of the main cylinder in a right and left symmetrical posture, a hole in an axial direction formed in the main cylinder 11 A is a vertically passing screw hole H 5 to which a thread M 4 of the reinforcing bars is screwed, end portion female screw holes H 6 , H 7 being concentric with the vertically passing screw hole H 5 and having a larger diameter than the vertically passing screw hole H 5 are formed in the inner holes of the right and left half bodies, end portion female screws F 6 , F 7 are provided in the end portion female screw holes H 6 , H 7 , the end portion female screws F 6 , F 7 have a phase that matches a phase of a female screw F 5 of the through hole H 5 , and have pitches P 6 , P 7 that are different from a screw pitch P 4 of the thread M 4 of the reinforcing bars 4 L, 4 R, the sub-cylinders 12 A, 13 A include sleeve portions 8 A, 9 A including end portion male screws M 8 , M 9 screwed to the end portion female screws F 6 , F 7 , and nut portions 14 A, 15 A being coaxial with the sleeve portions and formed integrally with one side ends of the sleeve portions, and the nut portions 14 A, 15 A are formed with nut portion female screws F 14 , F 15 to which the thread M 4 of the reinforcing bars 4 L, 4 R is screwed, the nut portion female screws F 14 , F 15 having a phase that matches a phase of the end portion male screws M 8 , M 9 . Here, in a case of (1) P 8 =P 14 +2 mm or P 9 =P 15 +2 mm, when the sub-cylinders 12 A, 13 A are separated from each other, galling occurs in P 14 , P 15 . In a case of (2) P 14 =P 8 +2 mm or P 15 =P 9 +2 mm, when the sub-cylinders 12 A, 13 A are caused to approach each other, galling occurs in P 8 , P 9 . Since P 4 ≢P 14 ≢P 15 and P 6 ≢P 7 ≢P 8 ≢P 9 are set, galling occurs in a chain reaction manner sometimes in meshing portions having a pitch difference excluding normal meshing portions. The followings can be understood from the above description. The reinforcing bars to be connected are bonded with equivalent components and can be fastened by torque loading operation in a similar manner. If the reinforcing bars have a thread within a molding tolerance, even when there is variation in the thread pitches, homogenization of fastening of reinforcing bars can be achieved. Since there is a difference in the pitch between the outer peripheral screws (or end portion female screws) of the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder and the thread of the reinforcing bar, a frictional force acting on a screw surface becomes large due to an increase in a screw surface contact pressure. When surface roughness of a screw thread occurs by pressurization, screw advancement or retreat thereafter is inhibited, so that galling occurs in a chain reaction manner sometimes in meshing portions having a pitch difference excluding normal meshing portions. Since the outer peripheral screw (or the end portion female screw) having a pitch larger than the pitch of the thread of the reinforcing bar is formed or the outer peripheral screw (or the end portion female screw) having a pitch smaller than the pitch of the thread of the reinforcing bar is formed in the outer periphery of the left half body and the outer periphery of the right half body of the main cylinder, it is possible to specify a screw to which a frictional force acting on the screw surface due to a surface pressure contact of the screw acts large, so that material selection of the main cylinder is facilitated. When a reaction receiving surface is formed on an outer surface of the through hole being a longitudinal center portion of the main cylinder, reaction receiving operation at the time of applying a desired torque to a polygonal nut portion is facilitated. When a slit extending in the axial direction is formed in the through hole being a longitudinal middle portion of the main cylinder, the distal end position of the inserted reinforcing bar can be checked. When another slit having the same shape as the slit is formed in a position facing the slit, viewing through is enabled and checking of the distal end position of the inserted reinforcing bar is facilitated. The through hole has been generally described to be a right-hand screw both in the left half body and the right half body. When the reinforcing bar is a left-hand screw, surface roughness is caused by operation of causing the sub-cylinders to reverse-rotate with respect to each other and approach each other. By providing a bending portion in the end portion in the side opposite to the coupler of the reinforcing bar, the reinforcing bar can have a fixation function. Although the fixation portion is planned in advance, it has an advantage that correspondence in a case where a change is required becomes rapid. Note that, in the present invention, there is no intention of excluding using of grout (mortar, adhesive, screw lock agent, or the like). That is, in the configuration of the present invention, introduction of grout or the like is not inhibited and injection of grout is considered to be unnecessary in principle in many cases. It is needless to say that grout can be used for locking in a known manner. The desired lock using galling can be achieved also in a configuration including a main cylinder and sub-cylinders in which females and males of screws of the main cylinder and sub-cylinders are inversed. REFERENCE NUMERALS 4 , 4 L, 4 R Threaded reinforcing bar M 4 Thread 4 Le Distal end of threaded reinforcing bar 6 , 7 Outer peripheral screw H 6 , H 7 End portion female screw hole F 6 , F 7 End portion female screw M 6 , M 7 End portion male screw 10 , 10 A Coupler 11 , 11 A Main cylinder 11 C Center body (reaction receiving surface) 12 , 12 A, 13 , 13 A Sub-cylinder H 5 Vertically passing screw hole F 5 Female screw 8 , 8 A, 9 , 9 A Sleeve portion F 8 , F 9 Sleeve inner peripheral screw M 8 , M 9 Sleeve portion male screw 14 , 14 A, 15 , 15 A Nut portion F 14 , F 15 Nut portion female screw 17 , 18 Slit 19 Gauge 21 , 22 Arrow to separation direction 23 , 24 Arrow to approach direction 25 Bending portion P 4 Pitch of thread in tolerable minimum molded article P 6 , P 7 Screw pitch of end portion male (or female) screw E Reinforcing bar end abutting space Q Threading attachment (spiral) start point in sub-cylinder U Angle reference point defining point Q θ Rotation angle at meshing start